The present invention relates to a loading cam device for a toroidal-type continuously variable transmission, an apparatus for measuring the thrust of such loading cam device, and a method for assembling a toroidal-type continuously variable transmission; and, in particular, the invention relates to a toroidal-type continuously variable transmission which is used as a change gear unit for a transmission for a vehicle, or as a transmission for various industrial machines.
Conventionally, it has been studied to use, as a transmission for a vehicle, such a toroidal-type continuously variable transmission as shown in FIGS. 11 and 12. In this toroidal-type continuously variable transmission, for example, as disclosed in Japanese Utility Model Publication No. Sho. 62-71465, an input side disk 2 is supported concentrically with an input shaft 1 and output disk 4 is fixed to the end portion of an output shaft 3 disposed concentrically with the input shaft 1. In the inside portion of a casing in which the toroidal-type continuously variable transmission is stored, there are disposed trunnions 6, 6 which are capable of swinging about their respective pivot shafts 5, 5 situated at torsional positions which respectively lie in a direction at right angle to the direction of the input and output shafts 1 and 3 but do not intersect the axes of the input and output shafts 1 and 3, as shown in FIGS. 11 and 12. That is, the trunnions 6, 6 respectively include the pivot shafts 5, 5 on the outer surfaces of their respective two end portions thereof in such a manner that the pivots 5, 5 are disposed concentrically with each other. Also, on the respective intermediate portions of the trunnions 6, 6, there are supported the base end portions of shift shafts 7, 7. Accordingly, by swinging the trunnions 6, 6 about the pivot shafts 5, 5, the inclination angles of the shift shafts 7, 7 can be freely adjusted. On the respective peripheries of the shift shafts 7, 7 which are supported on the trunnions 6, 6, there are rotatably supported power rollers 8, 8. And, the power rollers 8, 8 are respectively held by and between the mutually opposing inner surfaces 2a, 4a of the input side and output side disks 2, 4. The sections of the inner surfaces 2a, 4a are respectively formed in a concave-shaped surface which can be obtained by rotating an arc about the pivot shaft 5. And, the peripheral surfaces 8a, 8a of the power rollers 8, 8, which are respectively formed in a spherically convex-shaped surface, are respectively contacted with the inner surfaces 2a, 4a.
Between the input shaft 1 and input side disk 2, there is interposed a loading cam device 9. While the input side disk 2 is being elastically pressed toward the output side disk 2 by the loading cam device 9, the input side disk 2 can be freely rotated. The loading cam device 9 includes a cam plate 10 which can be rotated together with the input shaft 1, and a plurality of (for example, four) rollers 12, 12 which are rollably held by a retainer 11. On one side surface (in FIGS. 11 and 12, on the left side surface) of the cam plate 10, there is formed a drive side cam surface 13 which is an uneven surface extending in the circumferential direction of the cam plate 10; and, on the outer surface (in FIGS. 11 and 12, on the right side surface) of the input side disk 2, there is formed a driven side cam surface 14 having a similar shape to the drive side cam surface 13. And, the plurality of rollers 12, 12 are supported in such a manner that they can be freely rotated about their respective shafts extending in the radial direction with respect to the center of the input shaft 1.
When the above-structured toroidal-type continuously variable transmission is in operation, in case where the cam plate 10 is rotated with the rotation of the input shaft 1, the drive side cam surface 13 presses the plurality of rollers 12, 12 against the driven side cam surface 14 formed on the outer surface of the input side disk 2. As a result of this, at the same time when the input side disk 2 is pressed by the plurality of rollers 12, 12, the input side disk 2 is rotated due to the mutual pressing movements between the drive and driven side cam surfaces 13, 14 and the plurality of rollers 12, 12. And, the rotation of the input side disk 2 is transmitted through the plurality of power rollers 8, 8 to the output side disk 4, so that the output shaft 3 fixed to the output side disk 4 can be rotated.
To change a rotation speed ratio (change gear ratio) between the input and output shafts 1 and 3, firstly, when carrying out deceleration between the input and output shafts 1 and 3, the trunnions 6, 6 may be swung in a given direction about their respective pivot shafts 5, 5. And, the shift shafts 7, 7 may be inclined in such a manner that the peripheral surfaces 8a, 8a of the power rollers 8, 8, as shown in FIG. 11, can be respectively contacted with the near-to-center portion of the inner surface 2a of the input side disk 2 and the near-to-outer-periphery portion of the inner surface 4a of the output side disk 4. On the other hand, for acceleration, the trunnions 6, 6 may be swung in the opposite direction about their respective pivot shafts 5, 5. And, the shift shafts 7, 7 may be inclined in such a manner that the peripheral surfaces 8a, 8a of the power rollers 8, 8, as shown in FIG. 12, can be respectively contacted with the near-to-outer-periphery portion of the inner surface 2a of the input side disk 2 and the near-to-center portion of the inner surface 4a of the output side disk 4. In case where the inclination angles of the shift shafts 7, 7 are set in the intermediate angle between the inclination angles respectively shown in FIGS. 11 and 12, an intermediate change gear ratio can be obtained between the input and output shafts 1 and 3.
Also, FIGS. 13 and 14 show a more concrete example of a toroidal-type continuously variable transmission which is disclosed in Japanese Utility Model Publication No. Hei. 1-173552. An input side disk 2 and an output side disk 4 are rotatably supported on the periphery of a circular-pipe-shaped input shaft 15 respectively through needle roller bearings 16, 16. Also, a cam plate 10 is spline engaged with the outer peripheral surface of the end portion (in FIG. 13, the left end portion) of the input shaft 15, while a flange portion 17 prevents the cam plate 10 from moving in a direction to go away from the input side disk 2. And, the cam plate 10 and rollers 12, 12 cooperate together in forming a loading cam device 9 of a loading cam type which, in accordance with the rotation of the input shaft 15, rotates the input side disk 2 while pressing against the input side disk 2 toward the output side disk 4. To the output side disk 4, there is connected an output gear 18 through keys 19, 19 in such a manner that the output side disk 2 and output gear 18 are allowed to rotate synchronously with each other.
The respective two end portions of the pair of trunnions 6, 6 are supported on a pair of support plates 20, 20 in such a manner that they can be swung as well as can be shifted in the axial direction (in FIG. 13, in the front and back direction; in, FIG. 14, in the right and left direction) thereof. And, on circular holes 23, 23 portions which are respectively formed in the intermediate portions of the trunnions 6, 6, there are supported shift shafts 7, 7, respectively. And, these shift shafts 7, 7 respectively include support shaft portions 21, 21 and pivot sat portions 22, 22 which extend in parallel to each other but are eccentric with each other. Of these portions, the support shaft portions 21, 21 are respectively supported inwardly of their associated circular holes 23, 23 in such a manner that they can be freely rotated through radial needle roller bearings 24, 24. Also, on the peripheries of the pivot shaft portions 22, 22, there are rotatably supported power rollers 8, 8 through radial needle roller bearings 25, 25.
The pair of shift shafts 7, 7 are disposed at mutually 180.degree. opposite positions with respect to the input shaft 15. Also, a direction, in which the pivot shaft portions 22, 22 of the shift shafts 7, 7 are disposed eccentrically with respect to their associated support shaft portions 21, 21, is the same direction (in FIG. 14, in the reversed right and left direction) with respect to the rotation direction of the input side and output side disks 2 and 4. Also, this eccentric direction is a direction which intersects almost at right angles to the provision direction of the input shaft 15. Therefore, the power rollers 8, 8 are supported in such a manner that they are allowed to shift slightly in the provision direction of the input shaft 15. As a result of this, even in case where the power rollers 8, 8 tend to shift in the axial direction of the input shaft 15 (in FIG. 13, in the right and left direction; in FIG. 14, in the front and back direction) due to the elastic deformation of the component parts that are respectively elastically deformed by large loads applied thereto, such shift tendency of the power rollers 8, 8 can be absorbed without applying unreasonable forces to these component parts.
Also, between the respective outer surfaces of the power rollers 8, 8 and the respective inner surfaces of the intermediate portions of the trunnions 6, 6, there are disposed thrust ball bearings 26, 26 and thrust needle roller bearings 27, 27 sequentially in this order starting from the outer surface sides of the power rollers 8, 8. Of these bearings, the thrust ball bearings 26, 26 are bearings which, while supporting thrust-direction loads applied to the power rollers 8, 8, allow the power rollers 8, 8 to rotate. Each of the thrust ball bearings 26, 26 comprises a plurality of balls 29, 29, a circular-ring-shaped retainer 28 for holding the balls 29 in a freely rollable manner, and a circular-ring-shaped outer race 30. In each thrust ball bearing 26, its inner race raceway is formed in the outer surface of the power roller 8, while its outer race raceway is formed in the inner surface of the outer race 30.
Also, each of the thrust needle roller bearings 27, 27 includes a race 31, a retainer 32, and a plurality of needle rollers 33, 33. Of them, the race 31 and retainer 32 are combined together in such a manner that they are allowed to shift slightly in the rotation direction thereof. The thus structured thrust needle roller bearings 27, 27 respectively hold the races 31, 31 between the inner surfaces of the trunnions 6, 6 and the outer surfaces of the outer races 30, 30 while the races 31, 31 are respectively contacted with the inner surfaces of the trunnions 6, 6. The thrust needle roller bearings 27, 27 respectively support thrust loads applied from the power rollers 8, 8 to the outer races 30, 30 as well as allow the pivot shaft portions 22, 22 and outer races 30, 30 to swing about the support shaft portions 21, 21.
Further, to the one-end portions (in FIG. 14, the left end portions) of the trunnions 6, 6, there are connected drive rods 36, 36, respectively and, to the outer peripheral surfaces of the intermediate portions of these drive rods 36, 36, there are fixedly secured drive pistons 37, 37. And, these drive pistons 37, 37 are fitted into drive cylinders 38, 38 in an oil tight manner, respectively.
In the above-structured toroidal-type continuously variable transmission, the rotation of the input shaft 15 is transmitted through the loading cam device 9 to the input side disk 2. And, the rotation of the input side disk 2 is transmitted through the pair of power rollers 8, 8 to the output side disk 4, and further the rotation of the output side disk 4 is taken out by the output gear 18. To change a rotation speed ratio between the input shaft 15 and output gear 18, the pair of drive pistons 37, 37 may be shifted in the mutually opposite directions. With the shifting movements of the drive pistons 37, 37, the pair of trunnions 6, 6 are respectively shifted in the mutually opposite directions: for example, the power roller 8 situated on the lower side in FIG. 14 is shifted to the right in FIG. 14 and the power roller 8 situated on the upper side in FIG. 14 is shifted to the left in FIG. 14, respectively. This changes the direction of the tangential-direction forces that are applied to the contact portions between the peripheral surfaces 8a, 8a of the power rollers 8, 8 and the inner surfaces 2a, 4a of the input side disk 2 and output side disk 4. And, with such change in these forces, the trunnions 6, 6 are swung about the pivot shaft 5, 5 pivotally supported on the support plates 20, 20 in the mutually opposite directions. As a result of this, as shown in FIGS. 11 and 12, the contact positions between the peripheral surfaces 8a, 8a of the power rollers 8, 8 and the inner surfaces 2a, 4a of the input side disk 2 and output side disk 4 are respectively changed, thereby changing the rotation speed ratio between the input shaft 15 and output gear 18.
By the way, when transmitting the rotation force between the input shaft 15 and output gear 18 in this manner, the power rollers 8, 8 are shifted in the axial direction of the input shaft 15 due to the elastic deformation of the component parts, so that the shift shafts 7, 7 pivotally supporting the power rollers 8, 8 are rotated slightly about their respective support shaft portions 21, 21. As a result of this slight rotation, the outer surfaces of the outer races 30, 30 of the thrust ball bearings 26, 26 and the inner surfaces of the trunnions 6, 6 are caused to shift with respect to each other. A force necessary for this relative shift is small because the thrust needle roller bearings 27, 27 are interposed between the outer surfaces of the outer races 30, 30 of the thrust ball bearings 26, 26 and the inner surfaces of the trunnions 6, 6. Therefore, as described above, the inclination angles of the shift shafts 7, 7 can be changed by a small force.
Further, in order to be able to increase the torque that can be transmitted, conventionally, there is also known a structure in which, as shown in FIGS. 15 and 16, on the periphery of an input shaft 15a, there are disposed input side disks 2A, 2B and output side disks 4, 4 by twos, and these input side disks 2A, 2B and output side disks 4, 4 are arranged in parallel to each other with respect to the transmission direction of power. In either of the structures shown in FIGS. 15 and 16, an output gear 18a is supported on the periphery of the intermediate portion of the input shaft 15a in such a manner that the output gear 18a can be freely rotated with respect to the input shaft 15a, while the output side disks 4, 4 are respectively spline engaged with the two end portions of the cylindrical portion that is formed in the central portion of the output gear 18a. And, between the inner peripheral surfaces of the output side disks 4, 4 and the outer peripheral surface of the input shaft 15a, there are interposed needle roller bearings 16, 16, while the output side disks 4, 4 are respectively supported on the periphery of an input shaft 15a in such a manner that they can be rotated with respect to the input shaft 15a as well as they can be shifted in the axial direction of the input shaft 15a. Also, the input side disks 2A, 2B are respectively supported on the two end portions of the input shaft 15a in such a manner that they can be rotated together with the input shaft 15a. The input shaft 15a can be driven or rotated by a drive shaft 51 through a loading cam device 9. By the way, between the outer peripheral surface of the leading end portion (in FIGS. 15 and 16, the left end portion) of the drive shaft 51 and the inner peripheral surface of the base end portion (in FIGS. 15 and 16, the right end portion) of the input shaft 15a, there is interposed a radial bearing 52 such as a sliding bearing or a needle roller bearing. Therefore, the drive shaft 51 and input shaft 15a are combined together in such a manner that, while they remain disposed concentrically with each other, they are allowed to shift slightly in the rotation direction thereof.
Now, in one input side disk 2A (which is located on the left side in FIGS. 15 and 16), its back surface (the left surface in FIGS. 15 and 16) is butted directly (in the structure shown in FIG. 16) or through a countersunk plate spring 45 having large elasticity (in the structure shown in FIG. 15) against a loading nut 39 to thereby substantially prevent the input side disk 2A from shifting with respect to the input shaft 15a in the axial direction of (in FIGS. 15 and 16, in the right and left direction) of the input shaft 15a. On the other hand, the input side disk 2B disposed opposed to a cam plate 10 is supported by a ball spline 40 on the input shaft 15a in such a manner that it is allowed to shift in the axial direction of the input shaft 15a. And, between the back surface (in FIGS. 15 and 16, the right surface) of the input side disk 2B and the front surface (in FIGS. 15 and 16, the left surface) of the cam plate 10, there are interposed a countersunk plate spring 41 and a thrust needle bearing roller 42 in such a manner that they are connected in series to each other. Of them, the countersunk plate spring 41 plays a role to apply a pre-load to the contact portions between the inner surfaces 2a, 4a of the input side disks 2A, 2B and the peripheral surfaces 8a, 8a of the power rollers 8, 8. Also, the thrust needle roller bearing 42 has a function to allow the mutual relative rotation between the input side disk 2B and the cam plate 10 when the loading cam device 9 is in operation.
Also, in the structure shown in FIG. 15, the output gear 18a is rotatably supported by a pair of angular-type ball bearing 43, 43 on a partition wall 44 formed in the inside of the housing in such a manner that it is prevented against shift in the axial direction thereof. On the other hand, in the structure shown in FIG. 16, the output gear 18a is free to shift in the axial direction thereof. By the way, in a toroidal-type continuously variable transmission of a so called double cavity type in which, as shown in the above-described FIGS. 15 and 16, the input side disks 2A, 2B and output side disks 4, 4 are disposed by twos and arranged in parallel to each other with respect to the transmission direction of power, one or both of the input side disks 2A, 2B disposed opposed to the cam plate 10 is or are supported on the input shaft 15a by the ball spline 40, 40a so as to be free to shift in the axial direction of the input shaft 15a; and, the reason for this is to realize such condition that, while the two input side disks 2A, 2B can be rotated perfectly synchronously with each other, the two input side disks 2A, 2B are allowed to shift with respect to the input shaft 15a in the axial direction thereof in accordance with the elastic deformation of the component parts caused by the operation of the loading cam device 9.
The ball splines 40, 40a, which are disposed so as to realize the above object, respectively comprise inside diameter side ball spline grooves 46 respectively formed in the inner peripheral surfaces of the input side disks 2A, 2B, outside diameter side ball spline grooves 47 formed in the outer peripheral surfaces of the intermediate portions of the input shaft 15a, and a plurality of balls 48, 48 respectively interposed between the ball spline grooves 46, 47 in such a manner that they are free to roll. Also, the ball spline 40, which is used to support the input side disk 2B located on the loading cam device 9 side, secures a securing ring 50 to a securing groove 49 formed in the near-to-inner-surface 2a portion of the inner peripheral surface of the input side disk 2B to thereby prevent the plurality of balls 48, 48 from shifting to the inner surface 2a side of the input side disk 2B, which can thus prevent the balls 48, 48 from slipping out from between the inside diameter side and out-side diameter side ball spline grooves 46, 47. By the way, in the structure shown in FIG. 15, the ball spline 40a, which is used to support the input side disk 2A located on the side distant from the loading cam device 9, secures a securing ring 50a to a securing groove 49a formed in the outer periphery surface of the near-to-leading-end portion (in FIG. 15, the near-to-left-end portion) of the input shaft 15a to thereby prevent the plurality of balls 48, 48 from shifting to the inner surface 2a side of the input side disk 2A.
When assembling the above-structured toroidal-type continuously variable transmission, conventionally, the component parts thereof are assembled sequentially into the inside portion of a housing 53 (see FIG. 14) into which the main body of this toroidal-type continuously variable transmission is to be stored. Therefore, whether the component parts are shifted in position with respect to each other within the estimated dimensional errors thereof or not, and thus whether the component parts can function properly or not can be confirmed only after the component parts are all assembled into the housing 53.
On the other hand, to be able to secure the efficiency and durability of the toroidal-type continuously variable transmission, the position relationship between the component parts thereof must be maintained with high accuracy. For example, in order to be able to secure the above-mentioned efficiency and durability, it is important that the loading cam device 9 generates a given level of thrust as the cam plate 10 is rotated. For instance, in case where the thrust generated is excessively small, there run short the pressures of the contact portions between the inner surfaces 2a, 4a of the input side disks 2A, 2B and the peripheral surfaces 8a, 8a of the power rollers 8, 8 to thereby cause slippage in these contact portions, which in turn causes the toroidal-type continuously variable transmission to idle and thus fail to carry out power transmission. On the other hand, in case where the above thrust is excessively large, the pressures of the contact portions are excessively large, thereby resulting in the shortened rolling fatigue lives of the respective surfaces 2a, 4a, and 8a, 8a.
In view of the above, in case where the thrust generated from the loading cam device 9 in accordance with the estimated dimension errors and shape errors of the component parts of the toroidal-type continuously variable transmission deviates from the design value thereof, in order to reduce such thrust deviation by using other proper parts instead of the improper ones of the component parts, the toroidal-type continuously variable transmission, which has been assembled within the housing 53, must be taken apart to parts and assembled again.
In case where the assembling operation of the toroidal-type continuously variable transmission is carried out in this manner, it is troublesome to manufacture the toroidal-type continuously variable transmission, which makes it impossible to reduce the manufacturing cost thereof.